1. Field of the invention
The present invention relates to an RFID tag, and more particularly to an RFID tag capable of improving the recognition rate of the RFID and capable of recognizing a location of a certain RFID tag among a plurality of the RFID tags.
2. Description of the Prior Art
As generally known in the art, an RFID (radio frequency identification) system is the technology that can recognize an object using the radio communication, wherein a small semiconductor chip and an antenna connected to the small semiconductor chip are used to process the information of the object. Different from a barcode system recognizing only one object at a time, the RFID system has the advantage in that a number of the objects are recognized from a remote distance. The RFID system is currently used in a variety of field, such as a warehouse for storing products, the management of a special medicine, a supply network for military items, the management of the articles in a large-size market, and a traffic card. It is expected that the RFID system will be adopted in a multi-function electronic pay system for supplementing a function of a credit card in the future.
The RFID system includes: an RFID tag with a chip storing a variety of information and an antenna connected with the chip; and a reader supplying the current to the RFID tag and reading the information stored in the chip.
A passive type RFID tag does not have its own power source inside thereof, and thus the reader has to supply the power to the RFID tag using a continuous wave (CW). After receiving the power supply, the RFID tag modulates the continuous wave sent by the reader in the ASK (amplitude shift keying)/PSK (phase shift keying) manner and then transfers the modulated signal to the reader by backward-scattering. Accordingly, anybody can obtain the information stored in the RFID tag if the passive type RFID tag is supplied with the sufficient power.
In the meantime, when the RFID tag approaches the reader, the RFID tag performs the radio communication in response to the reader's request. Here, if a number of the RFID tags are within a range enabling the reader to perform the recognition, all of the RFID tags can be recognized instantly. However, the recognition rate, which is defined by the percentage of the RFID tags that can be recognized by the reader, cannot reach 100%, and a location of the recognized passive type RFID tag cannot be determined due to the interference between the RFID tags and the physical stacking of the RFID tags.